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    "story_id": "mp-2026-09-20-002",
    "source_story_id": "tmp-feature-3i-atlas-refractory-ice",
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    "headline": "The Interstellar Comet Carried Dirty Water Ice",
    "slug": "the-interstellar-comet-carried-dirty-water-ice",
    "dek": "JWST spectra favor tiny water-ice aggregates mixed with refractory material around 3I/ATLAS.",
    "summary": "JWST spectra favor tiny water-ice aggregates mixed with refractory material around 3I/ATLAS.",
    "body_text": "JWST/NIRSpec observed interstellar comet 3I/ATLAS at three epochs spanning eight months around perihelion. Its spectra show a broad three-micrometer absorption band together with water, carbon-dioxide and carbon-monoxide gas emission, but the shorter water-ice bands common in Solar System comae were weak or absent. Modeling favors submicron-to-micron water-ice-bearing aggregates mixed with refractory material. The final epoch also favors a second population of larger ice-rich grains and a subtle structure consistent with crystalline ice, though the authors say changing grain size and mixing can explain the evolution without requiring crystallization during the visit.",
    "why_it_matters": "JWST spectra favor tiny water-ice aggregates mixed with refractory material around 3I/ATLAS.",
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    "importance": 10,
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    "first_published_at": "2026-09-20T09:00:00.000-04:00",
    "modified_at": "2026-09-20T09:00:00.000-04:00",
    "content_status": "new",
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        "text": "JWST spectra favor tiny water-ice aggregates mixed with refractory material around 3I/ATLAS.",
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    "source_ids": [
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    "tags": [
      "3I/ATLAS",
      "JWST",
      "water ice"
    ],
    "image_url": "https://themachinepress.com/issues/2026-09-20/feature-3i-atlas-ice.png",
    "corrections": []
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  "sources": [
    {
      "source_id": "source-2026-09-20-002",
      "title": "arXiv preprint 2609.19286",
      "publisher": "arXiv",
      "url": "https://arxiv.org/abs/2609.19286",
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      "source_type": "primary_research",
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      "published_at": "2026-09-16T14:01:16.000-04:00",
      "accessed_at": "2026-09-20T08:23:59.913-04:00",
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    "name": "The Machine Press",
    "url": "https://themachinepress.com",
    "description": "A daily newspaper for the age of artificial intelligence."
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  "cite_this_report": {
    "title": "The Interstellar Comet Carried Dirty Water Ice",
    "publisher": "The Machine Press",
    "published_at": "2026-09-20T09:00:00.000-04:00",
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